Uveitis was induced in two monkeys by immunization with IRBP and serial fluorescein angiograms performed using different sized dextrans linked to fluorescein. The aim of these studies is to provide data on the retinal vessels and toxicology data to enable these agents to be used in humans. We have demonstrated that the larger molecular weight dextrans are less permeable than sodium fluorescein in the inflamed retina. The sites of large molecule leakage show ultrastructural evidence of open tight junctions whereas the areas that leak only sodium fluorescein have closed tight junctions.